How do i start making this character?
it depends what style do you wanna use? cartoon or real? high poly vs low poly?
here some references you should check (see the wireframe view to check how they model a similar mesh):


https://www.turbosquid.com/it/3d-models/3d-shake-nigiri-1401254
https://sketchfab.com/3d-models/handpainted-nigiri-sushi-combo-f3cd020bdad449b89afe9d21ed6fccc6
https://www.cgtrader.com/3d-models/food/miscellaneous/sushi-toro (metaballs for rice)